The use of intrabody medical equipment, such as endoscopes, catheters, and the like, for surgical, diagnostic and therapeutic purposes is rapidly expanding. To improve performance, the equipment has been optimized to best accomplish selected purposes. For example, endoscopes have been optimized and refined to provide upper endoscopes for examination of the esophagus, stomach, and duodenum; colonoscopes for the colon; angioscopes for blood vessels; bronchoscopes for the bronchi; laparoscopes for the peritoneal cavity; arthroscopes for joint spaces; nasopharyngoscopes for nasal passages and the pharynx; and intubation scopes for a person's airway.
A conventional endoscopic system 10, shown in FIG. 1, has an insertion tube 12 that is connected at a proximal end 14 to a handle or headpiece 16. The insertion tube 12 is adapted to be inserted into a patient's body to perform a selected surgical, therapeutic or diagnostic procedure. The endoscopic system 10 is generally manufactured with either a rigid or flexible insertion tube 12. The rigid insertion tube 12 maintains its shape to allow the operator to change the position of the portion of the insertion tube 12 that is within the body by applying torque to the portion of the endoscopic system 10 that is outside the body. The flexible insertion tube 12, on the other hand, cannot be controlled in such a manner. Instead, control wheels 24 are mounted on the headpiece 16 and connected to the insertion tube's distal end 20 by control cables (not shown). The control wheels 24 are manipulated to bend the insertion tube's distal end 20 to move the distal end 20 up, down, left, or right. Accordingly, the distal end 20 can be controlled to allow improved visibility or positioning of working tools within the patient's body.
The insertion tube 12 often contains an imaging system 18 having optical fibers or the like extending along the length of the insertion tube and terminating at a viewing window 19 in the insertion tube's distal end 20. The imaging system 18 conveys an image from the viewing window 19 to an eyepiece 22 on the headpiece 16, or to a monitor (not shown), so the user can see into a selected body cavity during an endoscopic procedure. Through manipulation of the control wheels 24, an operator can cause the distal end 20 of the insertion tube 12 to become substantially linear, or to take a curved shape to selectively position the viewing window 19.
The endoscopic system 10 also has an elongated working channel 32 extending from the proximal end 14 to the distal end 20 of the insertion tube 12. The working channel 32 is hollow along its length, and terminates in an opening 30 at the distal end 20 of the insertion tube 12. A working tool, such as a biopsy needle (not shown), to be used in a particular procedure is inserted into the working channel 32 from the proximal end 14 of the insertion tube 12 and threaded through the working channel 32. The working tool is manipulated at the headpiece 16 external to the patient to selectively project from the working channel's opening 30 in the patient during a procedure, such as when collecting samples of tissue. The working channel 32 can also be used to inject fluid into the patient or to create suction during a procedure. The endoscopic system 10 is described in greater detail in U.S. Pat. No. Re 34,110 and U.S. Pat. No. 4,646,722, which are incorporated herein by reference.
The illustrated endoscopic system 10, however, may not be suitable for all types of procedures. A cardiac catheter, for example, may be too narrow to contain both the working channel and imaging system, and may consequently be designed without an imaging system. The operator using such a cardiac catheter typically performs the procedure without direct visualization. The operator instead performs the procedure while the patient undergoes fluoroscopy, or with the help of an assistant, such as a cytologist, who performs cell assays on site to help determine whether the operator has located the desired area for the procedure.
Miniature location sensors have been developed to attach to the distal end of cardiac catheters and neuro probes to provide the operator with indirect visualization to determine the location of the distal end of the device inside the patient during the procedure. In indirect visualization, real time location information from the sensor is superimposed over a previously acquired CT or MRI model to illustrate to the operator the location of the distal end of the insertion tube with respect to the patient. Examples of such indirect visualization systems are described in more detail in U.S. Pat. Nos. 5,546,951 and 5,568,809, which are incorporated herein by reference.